1. Field of Invention
The present invention relates to wireless communication technology. More particularly, the present invention relates to a layout of a wireless communication circuit architecture on a printed circuit board (PCB), suitable for use as pPC-card for operating in the industrial, scientific and medical (ISM) band at 2.4 GHz.
2. Description of Related Art
In the last several decades, progress in radio and Very Large Scale Integrated circuit (VLSI) technology has fostered widespread use of radio communications in consumer applications. Portable devices, such as mobile radiotelephones, can now be produced having acceptable cost, size and power consumption.
Although wireless technology is today focused mainly on voice communications (e.g., with respect to handheld radios), this field will likely expand in the near future provide greater information flow to and from other types of nomadic devices and fixed devices. More specifically, it is likely that further advances in technology will provide very inexpensive radio equipment which can be easily integrated into many devices. This will reduce the number of cables currently used for many applications. For example, radio communication can eliminate or reduce the number of cables used to connect master devices with their respective peripherals.
The aforementioned radio communications will require an unlicensed band with sufficient capacity to allow for high data rate transmissions. A suitable band is the so-called Industrial, Scientific and Medical (ISM) band at 2.4 GHz, which is globally available. The ISM band provides 83.5 MHz of radio spectrum.
To allow different radio networks to share the same radio medium without coordination, signal spreading is usually applied. In fact, the Federal Communications Commission (FCC) in the United States currently requires radio equipment operating in the 2.4 GHz band to apply some form of spectrum spreading technique when the transmit power exceeds about 0 dBm. Spread spectrum communication techniques, which have been around since the days of World War II, are of interest in today's commercial applications because they provide robustness against interference, which allows for multiple signals to occupy the same bandwidth at the same time.
The use of cellular communication systems having mobile devices which communicate with a hardwired network, such as a local area network (LAN) or a wide area network (WAN), has become widespread. Retail stores and warehouse, for example, may use cellular communications systems with mobile data terminals to track inventory and replenish stock. The transportation industry may use such systems at large outdoor storage facilities to keep an accurate account of incoming and outgoing shipments. In manufacturing facilities, such systems are useful for tracking parts, completed products and defects. Such systems are also utilized for cellular telephone communications to allow users with wireless telephones to roam across large geographical regions while retaining telephonic access. Paging networks also may utilize cellular communications systems which enable a user carrying a pocket sized pager to be paged anywhere within a geographic region.
In order to manage the wireless communication with multiple nodes, the IEEE 802.11b protocol is proposed to govern the signal transmission and reception. Also and, since the computer industry is well developed, the wireless LAN (WLAN) has been allowed to be adapted in the computer system, such as person computer. For the application of IEEE 802.11b WLAN PC-CARD, traditional RF architecture of super-heterodyne is commonly adapted, which needs two voltage controlled oscillators (VCO), two mixers, and a surface acoustic wave (SAW) filter.
In order to reduce the fabrication cost, some elements are reduced. FIG. 1 is a block diagram, schematically illustrating the conventional wireless communication circuit architecture. From the circuit architecture in FIG. 1, the communication system at the local user″s system usually needs two antennas 100, 102 for diversity. During the receiving operation mode, one of the antennas 100, 102 with better quality can be selected for receiving the RF signals. However, one of the antennas 100, 102 can be set to be always used for transmission. The antennas 100, 102 are coupled to an antenna switch 104, which is used to select the desired antenna. The output of the antenna switch 104 is coupled to a band pass filter (BPF) 106. The BPF 106 allows the signal with specific frequency to pass. Particularly, the digital I/Q signal uses a specific frequency for transmission. Since the BPF 106 is commonly used for receiving mode and transmitting mode, the BPF 106 is coupled to transmission/receiving (T/R) switch 108. The T/R switch 108 has two output terminals one or for the receiving path and another one is for transmitting path. For the receiving path, the output signal from the BPF 106 is selected by the T/R switch 108 and sent to a RF integrated circuit (RFIC) 110. The RFIC 110 is used to convert the RF signal into the signal format capable of being processed, for example, in the local computer requested by the user. When a transmission mode is employed, the RFIC 110 sends the signal to a power amplifier 112. After being amplified, the signal is sent to a filter unit 114, which is composed by the BPF and the low pass filter (LPF). Then, the output of the BPF/LPF 114 is selected by the (T/R) switch 108 for transmitting. The signal then follows the same path for transmitting the RF signal.
In the foregoing conventional circuit architecture as shown in FIG. 1, the BPF 106 is typically necessary because the RFIC 110 usually includes a low noise amplifier (LNA), which needs the BPF 106 to filter away the noise. Also and, usually the RFIC 100 includes addition voltage controlled oscillator (VCO) (not shown) to reduce the frequency from high to low for internal circuit or other uses. Conventionally, it includes two VCO″s at lower frequencies. The VCO frequency should be filtered away. Therefore, the BPF/LPF 114 usually needs at least one BPF. When considering the whole range of the frequency, the LPF may also be included. Then, in the conventional design, the antennas 100, 102, the antenna switch 104 and the BPF 106 are commonly used in the transmitting path and the receiving path. From these considerations, the conventional wireless communication circuit architecture is designed as shown in FIG. 1.
From the performance point of view, since the transmitted signals will inevitably attenuates along with the transmitting distance, the transmission range in wireless communication is strongly concerned. The transmission range is then depending on the transmitting power. According to the convention design in FIG. 1, the insertion power loss for each elements are following. The antenna switch 104 consumes about 0.5 dB, the BPF 106 consumes about 2.0 dB, the T/R switch 108 also consumes 0.5 dB, and the BPF/LPF 114 at least also consumes about 2.0 dB, in which the LPF usually consume about 0.8 dB. In this design, the transmitting path needs two BPF″s to filter the signals. And, the BPF has larger power loss. In this design, the insertion loss is still not sufficient low. The skilled artisans may still intend to reduce insertion loss, so as to increase the transmission rage in wireless communication. How to improve the transmission range without consuming too much power is the issue to be solve or improved by the skilled artisans.